The present invention relates to a two-port valve for allowing and intercepting passage of fluid such as air, oil, water, and steam.
There is a known pilot-type two-port valve in which a pilot valve is switched to supply or discharge pressure fluid to and from a pressure operating chamber on one face side of a pressure-receiving body such as a piston and a diaphragm to move up and down the pressure-receiving body and a valve member connected to the pressure-receiving body through a valve stem to open and close a valve seat, thereby connecting and separating an input port and an output port for the pressure fluid to and from each other by opening and closing of the valve seat.
A known pilot-type two-port valve 100 shown in FIG. 4 as an example includes a main valve 101 having an input chamber 103 into which pressure fluid is introduced from an input port, an output port 104, a valve seat 105 in a flow path connecting the ports, and a valve member 106 for opening and closing the valve seat 105 and a pilot valve 102. In the main valve 101, the valve seat 105 is opened and closed by moving the valve member 106 up and down through a valve stem 107. A pressure-receiving body (a diaphragm in this example) 108 is secured to the valve stem 107 and the valve stem 107 is constantly pushed in a valve-closing direction by a return spring 109. The pressure-receiving body 108 is moved up and down by supplying and discharging the pressure fluid to and from the pressure operating chamber 110 by the pilot valve 102.
In the above known pilot-type two-port valve 100, a first stepped portion 114 and a second stepped portion 115 formed of shoulder portions and small-diameter portions extending in an axial direction are formed at a lower portion of the valve stem 107, an external thread is formed at an outer periphery of the small-diameter portion of the second stepped portion 115, the valve member 106 and a receiving plate 116 are respectively fitted over the small-diameter portions of the first stepped portion 114 and the second stepped portion 115, the valve member 106 is pushed against the shoulder portion of the first stepped portion 114 through the receiving plate 116 to mount the valve member 106 to the valve stem 107 by screwing a nut 117 over the small-diameter portion of the second stepped portion 115.
However, in this type of pilot-type two-port valve 100, because the valve member 106 is pushed against the valve stem 107 through the receiving plate 116 by screwing the nut 117 in mounting the valve member 106 to the valve stem 107, there are the following problems (1) to (4).
A two-port valve that is not the pilot type essentially has the similar problems.
(1) Because the valve member is fixed to the valve stem through the nut, it is difficult to obtain a satisfactory degree of parallelization of the valve member and the valve seat and airtightness is poor.
(2) Because it is necessary to screw the nut while fixing the valve stem, assembly is not easy and replacement of the valve member is not easy either.
(3) Because it is necessary to take measures against loosening of the nut and an assembly property and reliability are poor.
(4) It is necessary to subject the valve stem to thread cutting and rotation preventing processing and cost increases.
It is an object of the present invention to provide a two-port valve in which a deviation of a degree of parallelization of a valve member and a valve seat can be corrected automatically, which has excellent airtightness, in which assembly and replacement of the valve member are easy, which has excellent assembly property and reliability, and in which cost can be reduced.
To achieve the above object, a two-port valve of the invention comprises a valve body including an input port and an output port for pressure fluid, a valve seat in a flow path connecting the ports, and a valve member for opening and closing the valve seat, wherein a shaft for driving the valve member for opening and closing has at its tip end portion a shoulder portion, a small-diameter portion extending in an axial direction from the shoulder portion, and a groove portion which is formed in a vicinity of a tip end portion of the small-diameter portion and into which a snap ring is mounted, the valve member has a through hole into which the small-diameter portion of the shaft is inserted and an annular stepped portion formed by increasing a diameter of a portion of the through hole, and the stepped portion being mounted with a sealant for providing sealing between the shaft and the valve member, and the valve member is locked while being pushed against the shoulder portion by the snap ring mounted into the groove portion through the plate.
In the two-port valve of the invention, it is preferable that the stepped portion formed in the through hole of the valve member is formed by increasing the diameter of the through hole on a tip end side of the shaft and that the valve member is pushed against the shoulder portion through the sealant mounted to the stepped portion by the plate or that the shoulder portion of the shaft is tapered and a portion of the valve member pushed against the shoulder portion has a taper that is substantially similar to a taper of the shoulder portion.
The two-port valve may be a pilot-type two-port valve for driving a valve member with pilot fluid pressure, the valve member is connected to a piston driven for opening and closing of the valve seat through a shaft, and a pressure operating chamber to and from which the pilot fluid pressure is supplied and discharged is formed on one side face of the piston.
In mounting of the valve member and the shaft to each other in the two-port valve, the valve member is fitted over the small-diameter portion formed on the shaft, the sealant is mounted to the stepped portion of the valve member, and the plate fitted over the small-diameter portion pushes the valve member through the sealant to resiliently push the valve member against the shoulder portion of the shaft. In this state, a diameter of the snap ring is increased, the snap ring is fitted over the small-diameter portion, and the diameter of the snap ring is reduced in a position of the groove portion formed at the small-diameter portion to mount the snap ring into the groove portion.
Therefore, the valve member is locked by the snap ring mounted into the groove portion of the shaft in a state in which the plate presses the sealant against resilience of the sealant and pushes the valve member against the shoulder portion of the shaft.
By carrying out the operations in a reverse order, the valve member can be detached from the shaft.
As described above, because the valve member is not fixed to the shaft but is locked resiliently by the snap ring through the plate in the two-port valve of the invention, the valve member can be seated along the valve seat, a deviation of a degree of parallelization of the valve member can be corrected automatically, and the shaft is unnecessary to be subjected to thread cutting and rotation preventing processing of a nut.
The plate is locked by the snap ring, which provides measures against loosening. Because sealing is provided between the shaft and the valve member by the sealant mounted to the stepped portion of the valve member, sealing is reliable.